How to find out for sure the stone (diamond - moissanite) if different testers give different results and how is it possible?
Detectors of diamonds based on thermal conductivity of minerals practically do not distinguish a diamond from moissanite because of their practical coincidence of the values of thermal conductivity of these minerals.
When using detectors based on combined heat and electric conductivity indicators it is possible to reduce the error percentage but not to bring them to zero (some moissanites are defined as diamonds and vice versa), which is related to the electrochemical properties of some types of diamonds and moissanites with alloying additives.
Detectors based on the measurement of refractive index (refractometers and reflectometers) may "not notice" stones with a "thick" narrated diamond-like or diamond layer.
Absolute results (including "layer-by-layer" determination in the sample) are provided by Raman spectrometry, but the disadvantage of this method include the high cost of the instrumentation and software-analytical base.